Radiotherapy aims to deliver an ablative dose to the tumour with minimal normal tissue exposure. However, anatomical motion during treatment results in misalignment between beam and target, compromising treatment efficacy. An ideal motion management strategy is to reposition and reshape the beam aperture in response to instantaneous motion. There exists a need to provide an optimal deliverable beam pattern. For multileaf collimator (MLC) tracking based delivery, a systematic leaf adaptation method is desired.
Given an estimate of instantaneous motion, it is desirable to transform the planning beam according to the such motion to generate an ideal aperture. However, such an ideal aperture is often undeliverable, due to physical constraints such as finite MLC leaf widths, and more importantly, the paired leaf structure.
What is needed is an optimization framework that provides a deliverable MLC configuration that is closest to the ideal aperture, where closeness is defined rigorously as the cumulative cost in terms of underdose to target and overdose to healthy tissue.